1. Field of the Invention
The present invention relates to a touch panel, especially to a touch panel having a multi-layer structure in which layers of the structure are symmetrically distributed in accordance with refractive index.
2. Description of the Related Art
In recent years, many electronic devices, such as mobile phones and tablet personal computers, are equipped with a touch sensor function. A touch panel is used as an input/output interface where a user may slide his finger or a stylus on the touch panel to control an electronic device.
The touch sensing technologies used in the present touch panel may be different, wherein the capacitive touch sensing technology has become the most commonly used technology. With reference to FIGS. 1 and 2, FIG. 1 is a structural schematic view of a conventional capacitive touch panel, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1. The conventional capacitive touch panel mainly includes a glass substrate 9, a black matrix layer 93, multiple first electrodes 90, multiple second electrodes 91, multiple first connecting wires 98, multiple second connecting wires 99 and a protective layer 94. The black matrix layer 93 is formed on the periphery region of a surface of the glass substrate 9 so as to form a shading area. The first electrodes 90 are formed on the surface of the glass substrate 9 and are arranged in a matrix manner and are connected in serial along an X-axis direction by multiple first conductive wires 900. The second electrode 91 are formed on the surface of the glass substrate 9 and are arranged in a matrix manner, wherein the second electrodes 91 are respectively arranged between the first electrodes 90, and the second electrodes 91 are connected in serial along a Y-axis direction by multiple second conductive wires 910. The first electrodes 90 and the second electrodes 91 are connected to a peripheral control circuit respectively through the first connecting wires 98 and the second connecting wires 99. The protective layer 94 covers the black matrix layer 93, the first electrodes 90, the second electrodes 91, the first connecting wires 98 and the second connecting wires 99. With reference to FIG. 2, in order to prevent the first conductive wire 900 and the second conductive wires 910 from being in contact with each other, multiple bridge insulation members 92 are disposed between the first conductive wires 900 and the second conductive wires 910 at the intersections of the first conductive wires 900 and the second conductive wires 910, so that the first conductive wires 900 can be insulated from the second conductive wires 910.
In the foregoing capacitive touch panel, the insulatedly-crossed first electrodes 90 and second electrodes 91 can produce capacitors and thereby form a touch-sensing area. When a user uses his finger to touch the surface of the capacitive touch panel, the capacitance of the capacitor at the touch point will be changed such that the peripheral control circuit connected to the first electrodes 90 and the second electrodes 91 can locate the position of the finger touch from the change of capacitance.
During the production process of the foregoing touch panel, the black matrix layer 93 is first formed on the surface of the glass substrate 9, and then a transparent conductive layer is mounted on the surfaces of the glass substrate 9 and the black matrix layer 93 to form the first electrodes 90 and the second electrodes 91 through a patterning process. At this time the black matrix layer 93 at the periphery region has a thickness being larger than a thickness of the patterned transparent conductive layer in the touch-sensing area, and thereby creating a height difference at edges of the touch-sensing area. Thus, in the follow-up process of mounting the protective layer 94, a thickness of the protective layer 94 may change at the edges of the touch-sensing area and then cause a rainbow mura phenomenon to occur at the edges of the touch-sensing area due to light interference.
Furthermore, the bridge insulation members 92 which are only mounted at intersections of the conductive wires do not contribute to the mechanical performance of the touch panel. Besides, since the bridge insulation members 92 are usually made from photoresists having a refractive index of about 1.5, the refractive index of the bridge insulation members 92 is lower than the refractive index of the first electrodes 90 and the second electrodes 91, and thereby the conditions of refraction of light through the bridge insulation member 92 and through the electrodes are different, such that a user may easily see the outline of the wirings of the first electrodes 90 and the second electrode 91.
Therefore, it is necessary to provide a touch panel to overcome the problems existing in the conventional technology.